1. Field of the Invention
The invention relates to controlling the polarization of an optical signal including data signals. In particular the invention relates to a method and apparatus for controlling the polarization state of a laser.
2. Background Information
Real-time polarization control of optical signals is vital for the deployment of optical communications and switching applications as well as wavelength conversion and similar applications.
Current approaches for polarization control typically consist of a polarization rotation unit and a feedback control unit. The polarization rotation is implemented either electro-optically using faraday rotators, micro-electro-mechanical systems (MEMS), liquid crystal waveplates, Lithium Niobate waveguides and segments of polarization maintaining (PM) fibers or thermal-optically using polymer waveguides. These devices, however, cannot control a rapidly varying State of Polarization (SOP) because the feedback control time scale is in nanoseconds.